| TurboJPEG Java Wrapper |
| ====================== |
| |
| The TurboJPEG shared library can optionally be built with a Java Native |
| Interface wrapper, which allows the library to be loaded and used directly from |
| Java applications. The Java front end for this is defined in several classes |
| located under org/libjpegturbo/turbojpeg. The source code for these Java |
| classes is licensed under a BSD-style license, so the files can be incorporated |
| directly into both open source and proprietary projects without restriction. A |
| Java archive (JAR) file containing these classes is also shipped with the |
| "official" distribution packages of libjpeg-turbo. |
| |
| TJExample.java, which should also be located in the same directory as this |
| README file, demonstrates how to use the TurboJPEG Java API to compress and |
| decompress JPEG images in memory. |
| |
| |
| Performance Pitfalls |
| -------------------- |
| |
| The TurboJPEG Java API defines several convenience methods that can allocate |
| image buffers or instantiate classes to hold the result of compress, |
| decompress, or transform operations. However, if you use these methods, then |
| be mindful of the amount of new data you are creating on the heap. It may be |
| necessary to manually invoke the garbage collector to prevent heap exhaustion |
| or to prevent performance degradation. Background garbage collection can kill |
| performance, particularly in a multi-threaded environment (Java pauses all |
| threads when the GC runs.) |
| |
| The TurboJPEG Java API always gives you the option of pre-allocating your own |
| source and destination buffers, which allows you to re-use those buffers for |
| compressing/decompressing multiple images. If the image sequence you are |
| compressing or decompressing consists of images of the same size, then |
| pre-allocating the buffers is recommended. |
| |
| |
| Installation Directory |
| ---------------------- |
| |
| The TurboJPEG Java Wrapper will look for the TurboJPEG JNI library |
| (libturbojpeg.so, libturbojpeg.jnilib, or turbojpeg.dll) in the system library |
| paths or in any paths specified in LD_LIBRARY_PATH (Un*x), DYLD_LIBRARY_PATH |
| (Mac), or PATH (Windows.) Failing this, on Un*x and Mac systems, the wrapper |
| will look for the JNI library under the library directory configured when |
| libjpeg-turbo was built. If that library directory is |
| /opt/libjpeg-turbo/lib32, then /opt/libjpeg-turbo/lib64 is also searched, and |
| vice versa. |
| |
| If you installed the JNI library into another directory, then you will need |
| to pass an argument of -Djava.library.path={path_to_JNI_library} to java, or |
| manipulate LD_LIBRARY_PATH, DYLD_LIBRARY_PATH, or PATH to include the directory |
| containing the JNI library. |
